Scanning electron microscopic studies of differentiating spermatids and spermatozoa of the frog lung-fluke, Haematoloechus medioplexus, will be undertaken. Topographical changes during differentiation will be correlated with possible changes in patterns of lectin-binding surface receptors. Also, an attempt will be made to relate lectin-binding sites to microtubules beneath the cell surface, some of which are bridged to the inner membrane surface. Further, the unique cross-striated microtubules of lung-fluke spermatozoa are to be studied in detail using the transmission electron microscope, and indirect immunolabeling studies involving a tubulin antibody may provide clues to the distribution of unpolymerized tubulin during sperm differentiation. Ligation, electrophoretic, and immunolabeling studies with antibody to tubulin and actin will be employed in attempting to elucidate structural components associated with axoplasmic transport in crayfish nerve cord. Rat sciatic nerve will also be studied. The possibility of glia yields axon transfer of proteins in crayfish nerve cord will be evaluated by means of time course experiments involving ligation and EM autoradiography. Finally, stages in the assembly of both chromatographed (purified) and unchromatographed forms of bovine brain tubulin will be studied; both tannic acid and negatively-stained formed elements will examined from early and late stages in the polymerization sequence, and additional experiments are planned relating to the role of pH and tubulin associated proteins in modulating assembly of tubulin into complete microtubules having 13 wall protofilaments.